From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27C68C10F06 for ; Sun, 31 Mar 2019 12:21:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E942D20989 for ; Sun, 31 Mar 2019 12:21:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="CqX9jRGI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731260AbfCaMVv (ORCPT ); Sun, 31 Mar 2019 08:21:51 -0400 Received: from mail-lj1-f176.google.com ([209.85.208.176]:33989 "EHLO mail-lj1-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726873AbfCaMVu (ORCPT ); Sun, 31 Mar 2019 08:21:50 -0400 Received: by mail-lj1-f176.google.com with SMTP id j89so5644305ljb.1; Sun, 31 Mar 2019 05:21:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:openpgp:autocrypt:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=vb8ji+z2/qKt5D5DeFedtohmqm5g/R2LEzauO++lqbY=; b=CqX9jRGIeQByR5reKIxOwGdfbNw5ziaLzNYfhOtkVN9+VPoVLAhm6ZL/ieKEXUM33t 32kG5JnQzhH0e6NL1WSmUqFdGgeXPmp/9LxsT/TKGB/huu8Phzz/xVpyzGdRo6e8UATj 4JRalZFnxkvyFv1kPHtyer0SWVkSv6gFJFYHaE11uMllmW6+RT+skYANebdzEwwzfEae Y/e932+3ZCJ0oEBGFUYYCz7iQ6f7BZJqefiyP7z9WSvpwTrbcCyWUTuAVWsKgV4DJrxa aBnE6vW2j5IHZujlOopgNdvQyFHq9j3ZxxgJsZb6TfSrJBR4uxGBYT/DEB3ywmjjSYdo kvXA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:openpgp:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=vb8ji+z2/qKt5D5DeFedtohmqm5g/R2LEzauO++lqbY=; b=A01HVtoP6y6b8Jc2iYYsdvdxnnXmQOL5brGrSJr8pynbDiSwjkDw7zMVMA2RB4s9gg 40wZwTtTYLb5PpYG2sYVl/eJHDaPNJz4ZLIbJm1A2poSGCLtMQw66ZhY1t9ciivJuMww mj1dPMbL1h86MouIZSK1gNHsvMBOYY2hRnd2oRqKMEAMRQ0AA+0Z6mqVN4yfpHgDpH+s FGcD292LO6/ouCUGmOR2BzzD3zMCD9XDXih+sNrX7CWBpnDLQw479cpMyzOQ7Nyynvjg Th+c+zxQ/w3P3srNTqaNJ7vUyE1srBC+TT5aZpv1vi1wDZmrGOtZsZT+VYQClf3xlEWX sXGw== X-Gm-Message-State: APjAAAUKDI48bjuxTZX4CHwTRGqx91ebHOgG2Msh9G16AxQo1xBmLL9J Nqz2M2cJ5PgubOwDg/h2QA19Lv6Z X-Google-Smtp-Source: APXvYqym9kULuR1pBcuL6VUA5NG6BL224DK16AEOOTTi3i3ssrylc7TyiCvV8re8RHR+ecSXbG2OuA== X-Received: by 2002:a2e:a284:: with SMTP id k4mr28744509lja.99.1554034908257; Sun, 31 Mar 2019 05:21:48 -0700 (PDT) Received: from [192.168.1.5] ([109.252.90.193]) by smtp.gmail.com with ESMTPSA id t28sm1589795lje.9.2019.03.31.05.21.47 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 31 Mar 2019 05:21:47 -0700 (PDT) Subject: Re: Is it possible that certain physical disk doesn't implement flush correctly? To: Alberto Bursi , Qu Wenruo , "linux-btrfs@vger.kernel.org" , Linux FS Devel , "linux-block@vger.kernel.org" References: From: Andrei Borzenkov Openpgp: preference=signencrypt Autocrypt: addr=arvidjaar@gmail.com; prefer-encrypt=mutual; keydata= xsDiBDxiRwwRBAC3CN9wdwpVEqUGmSoqF8tWVIT4P/bLCSZLkinSZ2drsblKpdG7x+guxwts +LgI8qjf/q5Lah1TwOqzDvjHYJ1wbBauxZ03nDzSLUhD4Ms1IsqlIwyTLumQs4vcQdvLxjFs G70aDglgUSBogtaIEsiYZXl4X0j3L9fVstuz4/wXtwCg1cN/yv/eBC0tkcM1nsJXQrC5Ay8D /1aA5qPticLBpmEBxqkf0EMHuzyrFlqVw1tUjZ+Ep2LMlem8malPvfdZKEZ71W1a/XbRn8FE SOp0tUa5GwdoDXgEp1CJUn+WLurR0KPDf01E4j/PHHAoABgrqcOTcIVoNpv2gNiBySVsNGzF XTeY/Yd6vQclkqjBYONGN3r9R8bWA/0Y1j4XK61qjowRk3Iy8sBggM3PmmNRUJYgroerpcAr 2byz6wTsb3U7OzUZ1Llgisk5Qum0RN77m3I37FXlIhCmSEY7KZVzGNW3blugLHcfw/HuCB7R 1w5qiLWKK6eCQHL+BZwiU8hX3dtTq9d7WhRW5nsVPEaPqudQfMSi/Ux1kc0mQW5kcmVpIEJv cnplbmtvdiA8YXJ2aWRqYWFyQGdtYWlsLmNvbT7CZQQTEQIAJQIbAwYLCQgHAwIGFQgCCQoL BBYCAwECHgECF4AFAliWAiQCGQEACgkQR6LMutpd94wFGwCeNuQnMDxve/Fo3EvYIkAOn+zE 21cAnRCQTXd1hTgcRHfpArEd/Rcb5+SczsBNBDxiRyQQBACQtME33UHfFOCApLki4kLFrIw1 5A5asua10jm5It+hxzI9jDR9/bNEKDTKSciHnM7aRUggLwTt+6CXkMy8an+tVqGL/MvDc4/R KKlZxj39xP7wVXdt8y1ciY4ZqqZf3tmmSN9DlLcZJIOT82DaJZuvr7UJ7rLzBFbAUh4yRKaN nwADBwQAjNvMr/KBcGsV/UvxZSm/mdpvUPtcw9qmbxCrqFQoB6TmoZ7F6wp/rL3TkQ5UElPR gsG12+Dk9GgRhnnxTHCFgN1qTiZNX4YIFpNrd0au3W/Xko79L0c4/49ten5OrFI/psx53fhY vLYfkJnc62h8hiNeM6kqYa/x0BEddu92ZG7CRgQYEQIABgUCPGJHJAAKCRBHosy62l33jMhd AJ48P7WDvKLQQ5MKnn2D/TI337uA/gCgn5mnvm4SBctbhaSBgckRmgSxfwQ= Message-ID: <8faff75a-21bb-b21b-b19b-fd5aad002b88@gmail.com> Date: Sun, 31 Mar 2019 15:21:46 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org 31.03.2019 14:27, Alberto Bursi пишет: > > On 30/03/19 13:31, Qu Wenruo wrote: >> Hi, >> >> I'm wondering if it's possible that certain physical device doesn't >> handle flush correctly. >> >> E.g. some vendor does some complex logical in their hdd controller to >> skip certain flush request (but not all, obviously) to improve performance? >> >> Do anyone see such reports? >> >> And if proves to happened before, how do we users detect such problem? >> >> Can we just check the flush time against the write before flush call? >> E.g. write X random blocks into that device, call fsync() on it, check >> the execution time. Repeat Y times, and compare the avg/std. >> And change X to 2X/4X/..., repeat above check. >> >> Thanks, >> Qu >> >> > > Afaik HDDs and SSDs do lie to fsync() > > unless the write cache is turned off with hdparm, I know at least one case of SSD that are claimed to flush cache in case of power loss. I can dig up details if anyone is interested. > > hdparm -W0 /dev/sda > > similarly to RAID controllers. > > see below > > https://brad.livejournal.com/2116715.html > > https://queue.acm.org/detail.cfm?id=2367378 > > > - >